Optical communication networks include various optical switches or nodes coupled through a network of optical fiber links. One common method used for optical communications is a synchronous optical network (SONET). SONET networks are often comprised of optical rings with interconnecting nodes attaching to the rings. In common SONET networks, a bi-directional line-switch ring (BLSR) is used for interconnecting the rings and nodes of the optical network.
Carrying capacity in a SONET network may be increased without incurring additional installation costs by multiplexing multiple signals onto a single fiber using various methods, such as time division multiplexing (TDM), where two or more different signals are carried over the same fiber, each sharing a portion of time. Another multiplexing method is wavelength division multiplexing (WDM), in which two or more different wavelengths of light are simultaneously carried over a common fiber.
Wavelength division multiplexing can separate a fiber's available bandwidth into multiple channels. Dividing bandwidth into multiple discreet channels, such as 8, 16, 40, or even as many as 160 channels, through a technique referred to as dense channel wavelength division multiplexing (DWDM), is a relatively lower cost method of substantially increasing telecommunication capacity using existing fiber optic transmission lines. In a WDM network, optical signals of differing wavelengths are combined onto a common fiber-optic line or other optical waveguide and later are separated again into the individual signals or channels at the opposite end or other point along the fiber-optic cable.
With the advent and implementation of WDM, the reach of optical signals has increased significantly, with it now being possible to transmit an optical signal from coast to coast without requiring electrical signal regeneration. “Latency” refers to the time delay between an optical signal propagating through the network and a reference signal. Accurate latency measurements are beneficial to operators and subscribers of optical network services. Known latency measuring systems are based on a sum of known latencies attributable to each segment or element in a transmission line. Unfortunately, latency values for many optical components are not known or easily identified. Additionally, determining latency across a number of network links by summing known latency values for each component in each link typically does not result in a suitably accurate latency calculation.